child_process: support Uint8Array input to methods

Support `Uint8Array` input to all the synchronous methods.

PR-URL: https://github.com/nodejs/node/pull/10653


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michal Zasso <targos@protonmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>